Nodes of a local area network (LAN) are typically interconnected by a shared transmission medium. The amount of data traffic that the shared transmission medium can accommodate, however, is limited. For example, only one node at a time can successfully transmit data to another node over the shared transmission medium. If two or more nodes simultaneously attempt to transmit data, a data collision occurs, which tends to corrupt the data being transmitted. Thus, nodes that share a transmission medium are considered to be in a same collision domain.
A multi-port bridge allows simultaneous communication between nodes of the LAN by segmenting the LAN into multiple collision domains (also referred to as network segments), each segment having a corresponding transmission medium. FIG. 1 illustrates a conventional local area network (LAN) including a multi-port bridge 20. The multi-port bridge 20 in this example has eight ports A-H, though the number of ports can vary. Each port A-H is connected to a segment 21-28 of the LAN. Each segment 21-28 typically includes one or more nodes 29-44, such as a workstation, a personal computer, a data terminal, a file server, a printer, a facsimile, a scanner or other conventional digital device. Each of the nodes 29-44 has an associated node address which uniquely identifies the node. The nodes 29-44 are configured to send data, one to another.
When the LAN operates according to Ethernet standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard, data is communicated in the form of discrete packets. FIG. 2 illustrates a conventional IEEE 802.3 data packet 50. The data packet 50 has an eight byte long pre-amble 51 which is generally utilized for synchronizing a receiver to the data packet 50. The pre-amble 51 includes seven bytes of pre-amble and one bite of start-of-frame. Following the pre-amble 51, the data packet 50 includes a six byte long destination address 52, which is the node address of a node which is an intended recipient for the data packet 50. Next, the data packet 50 includes a six byte long source address 53, which is the node address of a node which originated the data packet 50. Then, following the source address 53 is a two-byte data type field 54. Following the data type field 54 is a data field 55. The data field 55 can be up to 1500 bytes long. In addition, the packet can include a two-byte length field between the source address 53 and data type field 54. Finally, the data packet 50 includes a four-byte frame check field 56 which allows a recipient of the data packet 50 to determine whether an error has occurred during transmission of the data packet 50.
When a node (source node) sends data to another node (destination node) located on its same segment of the LAN (intra-segment communication), the data is communicated directly between the nodes without intervention by the multi-port bridge 20 and is known as an intra-segment packet. Therefore, when the multi-port bridge 20 receives an intra-segment packet, the multi-port bridge 20 does not bridge the packet (the packet is filtered). When a node (source node) sends a data packet to another node (destination node) located on a different segment (inter-segment communication), the multi-port bridge 20 appropriately forwards the data packet to the destination node.
Accordingly, each port A-H of the multi-port bridge 20 receives packets from the network segment associated with the port, forwards the packets that are to be transmitted by another port, and also transmits packets to the network segment associated with the port. To achieve each of these functions, each port conventionally includes relatively complex circuitry, such as a micro-processor and its associated circuitry. This tends to result in production costs for such a multi-port bridge 20 that are higher than desired and also tends to result in the performance and reliability of the multi-port bridge 20 being lower than desired. Because the multi-port bridge 20 includes a plurality of ports, the complexity of each port is multiplied by the number of ports, thereby, exacerbating these problems.
Therefore, what is needed is improved technique for reducing the complexity of the ports in a multi-port bridge. Preferably, such an improved technique would enhance, rather than sacrifice, functionality and performance of the ports.